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Ricci

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Everything posted by Ricci

  1. Ricci's Skhorn Subwoofer & Files

    I finally had a chance to look at this in depth. A couple of things jumped out at me. The Skhorn sim is the old development sim from before the cab was built and measured. It really doesn't match the real world performance of the cab. A large part of it is due to the limitations of HR and a simple sims ability to account for everything that is happening inside a complex cabinet. Even the reworked HR sim I recently posted, while much much closer, isn't exact. There are only so many sections in HR, etc. This is one of those things where you do the best you can developing the prototype, take your best shot at it and hope the final product is a success. I hesitate to make exact comparisons between sims when one has been built and measured and the other has not due to this. With that said the Skhorn sim looks much different once the updated one is used and it changes most of the comparisons made by a large amount. Efficiency / power input / excursion / FR shape / etc. I noticed that the baffle size is listed as 1300x1900 in the Edge comparison above. That would be for a stack of 4 cabs if I am not mistaken. Is that being compared to a single Skhorn cab with a frontal area of 610x1372mm or a pair? 4 cabs is 3X the baffle area or stack size of a single Skhorn. I've attached a 2 cabs to 1 Skhorn comparison from Edge. It looks like about a half dB gain due to directivity of the larger baffle area at 50Hz and about 1dB around 85Hz. By using a larger baffle area to increase forward directivity there can be some gains made, but it takes large increases to get a single dB down in the 40-50Hz range. Using a bass stack with the largest frontal area possible will maximize those gains but as usual there are limits to what is possible or practical in most cases. Take something with a shape like the DTS10 as an extreme example of maximizing the baffle area. A quad stack of those will couple very well and provides an enormous amount of baffle area for each single cab, but frontal area of a quad stack would be gigantinormous and impractical in most situations.
  2. Bulding the Room2 listening room

    I agree with much of what you say. I've thought about this for a while. Frequency response of subwoofers should have an output rating attached with it to keep things honest. Otherwise you get things like tiny 10" powered subs claiming 14Hz extension and other nonsense like you mentioned. For subwoofers I would like to specify a "useful" range and not worry too much about +/-3dB or whatever. What I do worry about is how much output a subwoofer is capable of. In my opinion this must be attached to the FR rating. These days almost anything can be equalized flat to very low frequencies. Who cares if it gets flat down to 14Hz if it can only produce 75dB? The way this would be kept honest is by attaching a detailed output rating to the lowest useful extension claimed. Too much detail is overload, but not enough allows specsmanship, or gaming the system. Balancing the 2 is tricky. The output rating itself has to have all the details necessary to make it comparable and honest. It must note whether the output is calculated or measured, microphone distance, whether it is a peak reading and whether the environment is full, half, quarter-space, etc. Distortion such as via Don Keele's tone bursts would be nice, but not required. Also absolutely necessary is the frequency used for the output rating. This is what I would like to see used. It keeps things as simple as possible, but provides the necessary detail for some sort of quick comparison. The attached measurements are from the dual opposed 24" sealed cube with 21Ipal's and a SP1-6000 amp as an example. There is a raw FR and the distortion limited and maximum output bursts. I'm using this one as an extreme example since it is sealed and has ridiculous upper bass output which skews the raw FR by a huge margin. Clearly no one would run this system sans EQ. Almost any bass system these days will employ EQ for response shaping. Certainly any active / turn key sub system for sale. It would be quite easy to make this response shape flattish to an arbitrary low frequency. Say 20-150Hz +/-3dB for example. Let's call that the FR rating and assume that was done. There will be a limit to how loud the sub can be pushed before it starts to limit the low frequency output and the response shape is no longer maintained. In this case the all out max burst of the sub was measured at 113.7dB at 20hz. I'd like to see the output rounded to the nearest 0.5dB so as not to get into splitting data points of less than 0.5dB between units, so let's call it 113.5dB. I'd call this "minimum output" or something like that. Many subs will also define a useful frequency range which is a bit looser (sometimes +-10dB) and beyond the tighter FR spec. This being a rather high output sealed sub we could reasonably call the useful lower FR limit as 10Hz. Let's call the "useful FR" 10-150Hz. That being the case we should also specify the max output at 10Hz since it is claimed to be useful. That would be 102.2dB all out with no THD limit. Rounded down to 102dB. A maximum in band output would also be useful. as we all know it's much easier to make something really loud at 150Hz than at 15Hz. Personally I think all subwoofers should be rated at 63Hz or lower for maximum output. 63Hz is a legitimate bass frequency which will avoid cheating and using peaks in output up above 80Hz (or even an octave higher) for a "sub". If the sub has peak output at a lower frequency great, however the DB the measurements show that to be a very rare sub indeed. 63Hz is also high enough in frequency that any cab calling itself a "sub" should be able to hit it in bandwidth with power. In the case of this sub we would use the 63Hz burst which measured an even 130dB. The ratings for this sub would look like this. Frequency Response: 20-150Hz +/-3dB / Half-space / 2m (assuming after DSP of course) Minimum output with rated Frequency Response: 113.5dB SPL@20Hz / Half-space / 2m / Measured Useful Frequency Range: 10-150Hz Useful Low Frequency Output: 102dB SPL@10Hz / Half-space / 2m / Measured Maximum Output: 130dB SPL@63Hz / Half-space / 2m / Measured
  3. iPAL enclosure details

    I had thought that was the case. Well...Now it is confirmed.
  4. dbv2 feature complete

    It's the total man hours needed and room for errors that has me worried.
  5. Ricci's Skhorn Subwoofer & Files

    I finally DL'd this. I'll have a look at it when I get a chance. What model of subs were used?
  6. Ricci's Skhorn Subwoofer & Files

    Ok...Finally got time to write up a post. Went back and updated the HR sim data for the Skhorn. The original sims prior to measuring the final speaker were not such a good match. Turns out my choice of placement of S3, S4 and S5 with the limited amount of sections in HR were not all they could've been. Incorporating the air volume in the driver cones rather into S2, instead of using Vtc and Atc, was a much closer match for this design. The other big improvement was moving S3 to the smallest section, directly after the drivers and incorporating the large air volume in the final corners of the horn section into S4. Sim is much closer now. Still not perfect, but probably about as good as it will get using HR. I believe I have learned another couple of tricks to make HR sims for horns more accurate by revisiting this but I'll need to verify in a couple more cases to be sure it applies to more than just this cab. Took some more time and looked at the Edge program vs measurements and sims and it lines up very well. Looky there the math works! Here is the new HR input for the Skhorn. This is the GP measurement of the Skhorn cab at 14.1 volts (normalized back to 1.41v) compared with the same measurement with the baffle effects as calculated by Edge removed from the measurement. Here is the measured response, once again using the Edge program cal file from the above graph, compared with the improved HR sim. This is a good match. This is the same graph as above but with the original HR sim from back before the cab was measured added in as the blue line. It was not a very good match.
  7. dbv2 feature complete

    I'm scared...All that data to move over!
  8. Comments and discussion go here...Just put the measurement and driver notes up.
  9. iPAL enclosure details

    Single airspace. Cab was originally for 1 18"driver.
  10. Ricci's Skhorn Subwoofer & Files

    I've never been on social media. I need another time sink like a hole in the head.
  11. Ricci's Skhorn Subwoofer & Files

    That's a lot to respond to. Couple of things I noticed. You shouldn't use 1pi as an approximation for 2 cabs. It's better to cut the Skhorn in half or double the inputs for your single driver simulation. Also I noticed some of your inputs for the 21SW152-4 are off. Re should be 3.4. Also the original Skhorn sim isn't as close as it could be. The original inputs were as best I could guess at it feeding inputs from the cab design back into HR during the design phase, prior to building and measuring. I never went back and fit it better to the real result. I'm lazy! I do have some preliminary target sims for my single driver, half size Skhorn cab, but I've not had time to get so far as to design the cab. The final cab design process takes about 100X longer than and always modifies the simple HR sims. That's why I haven't gotten it done yet. That looks like a lot larger boost than I would guess off of such a minor difference in frontal area. Hopefully I'll get time to look at some of it more in depth.
  12. Ricci's Skhorn Subwoofer & Files

    Don't worry I'm in much the same boat. I've been avoiding using it for a long time. I'd love to see a few of the measurements. I also needed this handy directivity calculator in my toolbox. I've done some checking and it matches up very well with my measurements. What I've found is that even relatively small baffles like 20x20" have effects down to 40-50Hz and lower. There isn't a whole lot of change from there until the baffle size gets truly large. I believe the enclosure used for the SI 24" testing and the DTS-10 were the biggest frontal areas I've had. If I recall they were providing 1dB of lift way down at 30Hz if not a bit lower. I've subtracted out the directivity lift for the Skhorn calculated by Edge and the results are pretty close. I'm working on tweaking the sim a bit closer in HR based on this. The main thing I'm seeing is there is still a moderate 1-2dB lift in the 50-80Hz region that I cannot seem to get in HR. I'll post a revised HR input when I'm done.
  13. Xarion Laser Acoustics

    I'm just going to leave this here. Xarion.com I actually discovered this at work from a colleague believe it or not. We have components that are used in their products.
  14. Your best bet is to browse the catalogs of the major professional speaker companies. Covering 60-500Hz with a pro 12" should be relatively easy. There are probably a huge number of choices from Eminence, Faital, 18sound, BMS, Ciare, etc...That would all do quite well. Pick one that is readily available in your price range and that models well in the enclosure.
  15. Xarion Laser Acoustics

    Lots of things are spec'd to 10 or 20Hz but work pretty well lower than that. Hopefully this is one of those cases.
  16. Xarion Laser Acoustics

    I might inquire into the cost of one of these kits. Couldn't hurt to find out. What I like about this is the ability to handle extremely high pressures without any problem and the extremely small size. It would be useful for investigating inside of horns or bandpass cabs or other very close proximity high spl situations. I also like the idea that there are no moving parts, or diaphragm that reacts to physical forces with the associated resonances, etc. It removes one more source of potential variation from the signal chain. One thing that may be of concern is the laser head. This likely uses a small solid state laser so it could be engineered to last a good long while, or it may only last a few hundred hours. Depending on use you could be replacing the diode, or laser assembly once in 10 years or every year. Also lasers do not do well with shock, rapid temperature changes and humidity usually. That could be a concern. I'm speculating. They may have developed it around a very low cost, robust laser assembly.
  17. iPAL enclosure details

    That is the problem. I don't think I can get them from PS.
  18. iPAL enclosure details

    4 21's are in my 2 Skhorn cabs. Done... Ipalmod I'm not sure. Eventually want to do some comparative testing of with and without the feedback correction to document how much improvement it makes. May eventually get another plus the heatsinks and install them as plate amps in the Skhorns. I meant that finished M-force subs with a driver and module built in are available from a few companies. This would be one way to get the driver and module, without dealing with Powersoft engineering / support, but I'm not paying that much money.
  19. Ricci's Skhorn Subwoofer & Files

    The more detailed Akabak simulation that I have is a closer match. HR is great but it doesn't have enough segments and other options available to sim the more complex enclosures as well as I'd like. I should probably update my HR Skhorn record and see if I can get it closer to the measured result. As far as the sensitivity measuring much higher than the simulation that is common. Nearly every sub I've measured comes in at least a bit higher than the sensitivity from the sims would suggest. I have long suspected that directivity may be part of that. There are also all of those other intangibles, like the driver behaving slightly different than the small signal parameters, inductance effects, resonances inside the enclosure, vent behaviors, etc. Are you using ABEC3? Care to share a bit of your simulation? I find ABEC3 extremely tedious to use due to all of the scripting required, so I avoid it most of the time.
  20. Ricci's Skhorn Subwoofer & Files

    Welcome to the forum Moar!! Thanks for the link. I did not have that program.
  21. iPAL enclosure details

    I have one Ipal module and 4 21Ipal woofers. I have been unable to get an M-drive module or system so far. I haven't tried hard to do so though. I could purchase an off the shelf sub but I'm not paying that kind of money. Paul I did not know that it would run without a sensor connected if the feedback is set at the lowest setting. Good to know. Is this confirmed in the literature or did you try it? Awedio I talked with Nathan Funk about the Ipal mod years ago and he had tried it on a DO sealed system and managed to blow one up with sine waves below 15Hz. I've never tried it on a sealed system yet but he told me that it limited the power below 15Hz and did not do well dumping current into those frequencies with a 1ohm system. That's just what I heard.
  22. Ricci's Skhorn Subwoofer & Files

    I'll have to get back with you tomorrow on this once I'm on my PC and can look at it in more detail.
  23. Woofer for 40-250Hz?

    The BMS should be really clean. You don't see them used much due to cost and difficulty of getting them in the US. Should be a great driver though.
  24. iPAL enclosure details

    I believe it could work with a DO box like this with a single sensor, but it is possible that the slightly delayed and lower level output from the other driver may cause it to become unstable or go haywire. Would need to do verification testing. M-drive module is much more up my alley...Unfortunately very difficult to get. Also note that the modules will not produce any amplification at all unless the DPC sensor is detected. It will not operate with out a sensor for each module.
  25. Xarion Laser Acoustics

    I do not know how much these are. I just found out about this product on Monday. I expect it is many thousands of USD or EU. The 250 model specs a dynamic range of 50-150dB and a low noise floor. Might be useful for typical 65-130dB acoustic measurements.
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